Those mesmerizing blue and orange hues in the sky at the start and end of a sunny day might have an essential role in setting humans’ internal clocks. A novel LED light that emits alternating wavelengths of orange and blue outpaced two other light devices in advancing melatonin levels in a small group of study participants. The finding appears to establish a new benchmark in humans’ ability to influence their circadian rhythms, and reflects an effective new approach to counteract seasonal affective disorder (SAD).